NaCl Particles Research Articles

Constructing salt-resistant 3D foams with hierarchical interconnected channels by vacuum casting method for efficient solar evaporation of hypersaline water

Solar interfacial water evaporation is an environmentally friendly and potential approach to producing fresh water. Herein, a PAN/CNTs-foam (PCF) evaporator with high porosity, hierarchical pore structure, and excellent solar absorption was successfully prepared by the vacuum casting method. The PCF prepared with a CNTs content of 17 % and NaCl particle size of 150–300 μm possessed an evaporation rate of 2.04 kg m−2 h−1 for pure water under 1 sun illumination. The PCF-2 showed a maximum evaporation rate of 5.60 kg m−2 h−1 for real seawater in outdoor experiments, and the quality of the produced clean water was also demonstrated. The purification ability of PCF for organic dyes further confirmed the potential usage in wastewater treatment. Particularly, the PCF-2 exhibited efficient and stable desalination performance for hypersaline water even in 25 wt% simulated brine due to the hierarchical interconnected channels. Our work offers a robust method for the construction of a 3D foam evaporator with hierarchical interconnected channels for efficient and sustainable hypersaline water desalination.

Photoactivation of Chlorine and Its Catalytic Role in the Formation of Sulfate Aerosols.

We present a novel mechanism for the formation of photocatalytic oxidants in deliquescent NaCl particles, which can greatly promote the multiphase photo-oxidation of SO2 to produce sulfate. The photoexcitation of the [Cl--H3O+-O2] complex leads to the generation of Cl and OH radicals, which is the key reason for enhancing aqueous-phase oxidation and accelerating SO2 oxidation. The mass normalization rate of sulfate production from the multiphase photoreaction of SO2 on NaCl droplets could be estimated to be 0.80 × 10-4 μg·h-1 at 72% RH and 1.33 × 10-4 μg·h-1 at 81% RH, which is equivalent to the known O3 liquid-phase oxidation mechanism. Our findings highlight the significance of multiphase photo-oxidation of SO2 on NaCl particles as a non-negligible source of sulfate in coastal areas. Furthermore, this study underscores the importance of Cl- photochemistry in the atmosphere.

Green preparation of water-stable coptidis-dyeing composite nanofiber filters with ultraviolet shielding and antibacterial activity and biodegradability

Particulate matter pollution and bacteria in the air have become hot topics due to their serious transmissibility and harm. Personal protection with respiratory masks was essential for our daily lives, but the reliability of commercial masks was limited by environmental factors, bacteria contamination, and non-degradability. Here, we prepared coptidis-dyeing polyvinyl alcohol (PVA)/polyacrylic acid (PAA) composite nanofiber filters with ultraviolet (UV) shielding, antibacterial activity, and biodegradability. The water stability of membranes was controlled using a green electrospinning-heat treatment process, improving the durability of masks in high humidity. The functionalization of composite nanofiber membranes was given through different coptidis-dyeing methods for the first time. The dyed membranes could maintain filtration efficiency of above 98 % against various NaCl particles (diameter of 0.225–7.25 μm) with a pressure drop of 196 Pa under a test flow rate of 32 L/min. Even at 85 L/min, the membrane could also maintain an interception efficiency of over 95 %, while the air resistance was below 343.2 Pa, meeting the requirements of GB 19083-2010 medical protective mask technology. Due to the natural functional properties of coptidis, the dyed membranes exhibited excellent antibacterial activity against Staphylococcus aureus of 99.8 % and a good UV protection index (UPF) of 286, respectively. The multifunctional dyed membranes are expected to become a filter layer that replaces the traditional melt-blown layer, providing insights to advance personal protective equipment.

3D PRINTING OF PCL TO FABRICATE POROUS SCAFFOLDS FOR BONE TISSUE ENGINEERING APPLICATIONS

The aim of this study is to print 3D polycaprolactone (PCL) scaffolds at high and low temperature (HT/LT) combined with salt leaching to induced porosity/larger pore size and improve material degradation without compromising cellular activity of printed scaffolds. PCL solutions with sodium chloride (NaCl) particles either directly printed in LT or were casted, dried, and printed in HT followed by washing in deionized water (DI) to leach out the salt. Micro-Computed tomography (Micro-CT) and scanning electron microscope (SEM) were performed for morphological analysis. The effect of the porosity on the mechanical properties and degradation was evaluated by a tensile test and etching with NaOH, respectively. To evaluate cellular responses, human bone marrow-derived mesenchymal stem/stromal cells (hBMSCs) were cultured on the scaffolds and their viability, attachment, morphology, proliferation, and osteogenic differentiation were assessed. Micro-CT and SEM analysis showed that porosity induced by the salt leaching increased with increasing the salt content in HT, however no change was observed in LT. Structure thickness reduced with elevating NaCl content. Mass loss of scaffolds dramatically increased with elevated porosity in HT. Dog bone-shaped specimens with induced porosity exhibited higher ductility and toughness but less strength and stiffness under the tension in HT whereas they showed decrease in all mechanical properties in LT. All scaffolds showed excellent cytocompatibility. Cells were able to attach on the surface of the scaffolds and grow up to 14 days. Microscopy images of the seeded scaffolds showed substantial increase in the formation of extracellular matrix (ECM) network and elongation of the cells. The study demonstrated the ability of combining 3D printing and particulate leaching together to fabricate porous PCL scaffolds. The scaffolds were successfully printed with various salt content without negatively affecting cell responses. Printing porous thermoplastic polymer could be of great importance for temporary biocompatible implants in bone tissue engineering applications.

Ion imaging of spatially inhomogeneous nanoplasmas in NaCl particles.

Studying photoemission from free, unsupported aerosol particles is a powerful method for gaining insight into light-matter interactions at the nanoscale. We used single-shot velocity map imaging to experimentally measure kinetic energy and angular distributions of ions emitted following interaction of sub-micrometer NaCl particles with femtosecond pulses of near infrared (NIR, 800 nm) and ultraviolet (UV, 266 nm) light. We combined this with time-dependent simulations of light propagation through the particles and a rate equation approach to computationally address the origin of the observed ion emission. For both NIR and UV pulses, ion emission is caused by the formation of an under-dense nanoplasma with similar densities, although using an order of magnitude weaker UV intensities. Such conditions result in remarkably similar ion fragments with similar kinetic energies, and no obvious influence of the plasma formation mechanism (photoionization or collisional ionization). Our data suggests that Coulomb explosion does not play a significant role for ion emission, and we discuss alternative mechanisms that can lead to material ablation from under-dense nanoplasma. Finally, we show how finite size effects play an important role in photoemission through generation of spatially inhomogeneous nanoplasmas, which result in asymmetric ion emission that depends on particle size and laser wavelength. By utilizing the single-particle information available from our experiments, we show how finite size effects and inhomogeneous nanoplasma formation can be exploited to retrieve the size and orientation of individual submicrometer aerosol particles.

Bio-inspired facile strategy for programmable osmosis-driven shape-morphing elastomer composite structures.

Achieving programmable and reversible deformations of soft materials is a long-standing goal for various applications in soft robotics, flexible electronics and many other fields. Swelling-induced shape morphing has been intensively studied as one of the potential mechanisms. However, achieving an extremely large swelling ratio (>1000% in volume) remains challenging with existing swellable soft materials (e.g., hydrogels and water-swellable rubbers). Inspired by the shape change enabled by the osmosis-driven swelling in living organisms, herein, we report a polymer composite system composed of fine sodium chloride (NaCl) particles embedded in Ecoflex00-10 polymer. This Ecoflex00-10/NaCl polymer composite can achieve controllable volumetric swelling up to 3000% while maintaining a relatively high elastic stiffness. We demonstrate that this swellable polymer composite can serve as an active component to drive the shape morphing of various structures. By controlling the geometric design and the fraction of the NaCl particle, morphing structures capable of deforming sequentially are created. Finally, by encapsulating 3D printed polymer composite patterns using water-permeable PDMS membrane, a programmable braille with visual and tactile regulation is demonstrated for the purpose of information encryption. Our study provides a facile approach to generate customizable shape-morphing structures, aiming to broaden the range of techniques and applications for morphing devices.

Preparation and in vitro degradation behavior of biodegradable porous Zn-Li-Ca alloy bone repair scaffolds

Porous pure Zn alloy scaffolds are often used for bone defects, but their clinical effects are limited due to poor mechanical properties and uneven degradation. In this study, porous Zn-Li-Ca alloy scaffolds with 70 % porosity were prepared by pressure infiltration method with 450–600 μm NaCl particles were used as pore-making agent. The effect of pore structure and the content of Ca element on, mechanical properties, degradation and weight loss of porous Zn alloy scaffolds soaked in simulated body fluids (SBF) for 4 weeks were studied. The results showed that the Zn alloy scaffolds prepared by spherical sodium chloride has high pore connectivity, and the yield strength and elastic modulus of Zn-0.8Li-0.8Ca reach 35.80 ± 1.89 MPa and 2.45 ± 0.19 GPa, respectively. Compared with the pure Zn alloy scaffolds, the yield strength was increased by 18.5 times, the elastic modulus was increased by 9 times, which meets the mechanical requirements of human cancellous bone. Compared with Zn-0.8Li alloy scaffolds, the weight loss rate and degradation rate at 4 weeks reached 7.51 % and 0.21 mm/y, respectively. In vitro studies showed that the addition of Ca element weakened the formation of Li2CO3 protective layer and accelerated the degradation rate of the scaffold. The problem of slow degradation rate of Zn-Li alloy was solved, which laid a foundation for subsequent in vivo implantation experiments. The results of this study indicate that the porous biodegradable Zn-based scaffold has great application potential in bone defects.

Research on topological effect of natural small molecule and high–performance antibacterial air filtration application by electrospinning

The application of natural small molecule (NSM) in electrospun fibers is the key to achieving powerful functionality and sustainable development. However, the lack of understanding regarding the mechanism for loading NSM hinders the advancement of high–performance functional fibers. This work clarified the loading mechanism of NSM in polymer solution by comparing the different behaviors of curcumin (Cur), phloretin (PL), and tea polyphenols (TP) blended ethyl cellulose (EC) solutions. We found that TP may lead to the folding of polymer chains due to its strongest hydrogen bond, which in turn promoted the dispersion of TP along the polymer chain. Therefore, TP could achieve good electrospinnability at the highest loading capacity (16 times the Cur and 4 times the PL). Finally, chitosan was introduced into EC/TP to prepare tree–like nanofibers, achieving high–performance antibacterial air filtration. The filtration efficiency for 0.3 μm NaCl particles, pressure drop, and quality factor were 99.991 %, 85.5 Pa, and 0.1089 Pa−1, respectively. The bacteriostatic rates against Escherichia coli and Staphylococcus aureus were all 99.99 %. This work will promote the application of NSM and the developments of multifunctional electrospun fibers and high–performance air filters.

Ethyl cellulose/gelatin/β–cyclodextrin/curcumin nanofibrous membrane with antibacterial and formaldehyde adsorbable capabilities for lightweight and high–performance air filtration

Functionalization of bio–based nanofibers is the development tendency of high–performance air filter. However, the conventional structural optimization strategy based on high solution conductivity greatly hinders the development of fully bio–based air filter, and not conducive to sustainable development. This work fabricated fully bio–based nanofibrous membrane with formaldehyde–adsorbable and antibacterial capabilities by electrospinning low–conductivity solution for high–performance air filtration and applied to lightweight mask. The “water–like” ethyl cellulose (EC) was selected as the base polymer to “nourish” functional materials of gelatin (GE), β–cyclodextrin (βCD), and curcumin (Cur), thus forming a solution system with high binding energy differences and electrospinning into ultrafine bimodal nanofibers. The filtration efficiency for 0.3 μm NaCl particles, pressure drop, and quality factor were 99.25 %, 53 Pa, and 0.092 Pa−1, respectively; the bacteriostatic rates against Escherichia coli and Staphylococcus aureus were 99.9 % and 99.4 %, respectively; the formaldehyde adsorption capacity was 442 μg/g. This is the first report on antibacterial and formaldehyde–adsorbable high–performance air filter entirely made from bio–based materials. This simple strategy will greatly broaden the selection of materials for preparing high–performance multifunctional air filter, and promote the development of bio–based air filter.

Synthesis and immobilization of HC/BiVO4 catalyst particles with PTFE for photocatalytic tetracycline degradation: Preparation, performance and mechanism

The hydrothermal carbon/bismuth vanadate (HC/BiVO4) composite catalyst particles were prepared by one-step hydrothermal process. For effective and convenient photocatalytic organics degradation, the sandwich-like immobilization of HC/BiVO4 particles was performed utilizing polytetrafluoroethylene (PTFE) as an adhesive agent, NaCl as a pore-creating agent and PTFE/graphite composite as the interlayer. The obtained results indicated that HC/BiVO4 exhibited the higher performance than the pure BiVO4 towards photocatalytic tetracycline degradation owing to its enhanced separation of electron-hole (e−-h+) pairs as well as relatively higher electron transfer ability. Four active species including superoxide anion radical (O2−), h+, hydroxyl radical (OH) and singlet oxygen (1O2) could be identified from the developed photocatalytic system, whereas O2− played the predominant role in tetracycline degradation. It was found that the immobilized photocatalyst owned a certain photocatalytic degradation activity, fine renew-ability and high mechanical strength. The pore-creating function of NaCl particles enhanced the immobilized photocatalyst's photocatalytic performance evidently. The photocatalytic treatment of tetracycline solution by the immobilized catalyst presented the removal efficiency of over 90 % in 120 min. In addition, after the degradation, the biodegradability of the solution was enhanced evidently due to the generation of readily biodegradable organic intermediates. This study mainly presents a new method to prepare the immobilized HC/BiVO4 photocatalyst promoting the application of photocatalytic technology in organic wastewater treatment.

Extraction and Characterization of Natural Coagulant Made from Banana Plant Stems (Musa acuminate) for the Removal of Turbidity from Wastewater

Wastewater treatment with chemical coagulants has a variety of drawbacks, including sludge management, cost, concerns for human health, and environmental pollution. In light of this, a study was conducted to determine whether banana plant stem (Musa acuminate) made coagulant can effectively reduce turbidity (NTU) of wastewater. In this study, conventional extraction method was used to extract the coagulant from the banana plant stem by using NaCl (0.1, 0.5, 1 M) solvent. After extraction, the coagulation efficiency of each produced coagulant was computed in terms of their turbidity removal efficiency (%) from sampled wastewater. The sampled wastewater had an average turbidity value of 893 NTU. Response surface methodology (RSM) and central composite design (CCD) were used to study the effects of NaCl solvent concentration (M), extraction time (min), and particle size (mm) on the coagulation efficiency (%) of the extracted coagulant. In addition, the coagulant was characterized such as FTIR analysis, point of zero charge value determination, and inulin compound presence analysis. From all prepared coagulants, the maximum coagulation efficiency obtained was 86.3% at the optimum conditions, such as 0.55 M (NaCl) of solvent concentration, 1.25 mm particle size, and 20 min of extraction time. The characterized coagulant had 6.2 points of zero charge value and also had various types of functional groups. Based on the findings of this study, it can be said that the coagulant prepared from banana stems (Musa acuminate) was an efficient natural coagulant that could be applied to treat wastewater.

Theoretical Investigation of Inorganic Particulate Matter: The Case of Water Adsorption on a NaCl Particle Model Studied Using Grand Canonical Monte Carlo Simulations

Sodium chloride (NaCl) represents the principal component of atmospheric particulates of marine origin. To gain a molecular-level understanding of the adsorption process of water vapor on the NaCl surface, Monte Carlo simulations performed in the Grand Canonical ensemble were carried out, considering the water adsorption at different water pressures on a NaCl(001) surface. The calculated adsorption isotherm shows four different regions, whose coverages correspond to those of the low-, transition-, high-, and pre-solution-coverage regions experimentally observed. Detailed analysis reveals how the structure of the adsorbed water molecules (islands, layer, and multi-layer) changes depending on water pressure, and how their orientation with respect to the surface varies with the distance from the surface. This detailed information further supports the picture coming from previous experimental IR absorption spectroscopy studies.

Supersonic nozzle performance prediction considering the homogeneous-heterogeneous coupling spontaneous non-equilibrium condensation

Supersonic nozzles are widely applied in steam turbines and other industrial fields. Condensation occurs due to rapid expansion of steam flowing through a sonic nozzle. The process is affected by the presence of steam impurities. The primary purpose of this study is to investigate the impact of different heterogeneous particles (solid particles, tiny droplets and NaCl particles) at different concentrations on the non-equilibrium condensing flow, and to classify and calculate condensation losses and total static isentropic efficiency resulting from the non-equilibrium condensation phenomenon. First, the proposed non-equilibrium condensation model is estimated numerically using the Barschdorff nozzle, and the model accuracy is validated by comparing the results with existing experimental data. Second, the effect of different particle concentrations on several condensing flows is studied using the Barschdorff nozzle. The results show that homogeneous condensation will get weaker with an increase in the particle concentration in the vapour condensing flow with solid particles and NaCl particles. Moreover, homogeneous condensation will be slightly enhanced first and then weakened with an increase in the particle concentration in the vapour condensing flow with tiny droplets. The steam condensing flow with different heterogeneous particles at the same particle concentration and the process of pure steam condensation are analysed. The results show that impurity particles in steam have a significant impeding effect on the process of homogeneous condensation. The losses are classified in the Barschdorff nozzle, and the magnitude of the losses and the flow total static isentropic efficiency are estimated. As the particle concentration increases from 1014[1/kg] to 1015[1/kg], the total static isentropic efficiency of solid particles and tiny droplets increases by 12.8 % and 9.6 %, respectively, while the total static isentropic efficiency of NaCl particles decreases by 27.2 %. This indicates that an appropriate increase in the particle concentration can effectively reduce condensation losses and improve total static isentropic efficiency. The paper describes the effect of heterogeneous particles on the steam condensing flow, providing a reference for future research on heterogeneous condensation processes.

Efficacy of BREATHOX® Device Inhalation on Acute Symptoms Associated with COVID-19 (BREATH Study): A Randomized Pilot Clinical Trial.

(1) Background: A high concentration of sodium chloride on in vitro cell culture leads to reduced SARS-CoV-2 replication. Therefore, our aim was to evaluate the effects of inhaling hypertonic NaCl particles (BREATHOX®) on the duration of COVID-19-induced acute symptoms. (2) Methods: A prospective, open label, randomized, standard of care-controlled group (SOC) pilot trial compared inhaled oral and nasal administered BREATHOX® (2.0 mg NaCl, particles size between 1-10 μm), with five or ten inhalations per day for ten days. The primary endpoint was the time to resolve COVID-19-related symptoms. Safety outcomes included adverse clinical and laboratory events. (3) Results: A total of 101 individuals were screened and 98 were randomly assigned to BREATHOX® ten sessions per day (Group 1; 33 patients), BREATHOX® five sessions per day (Group 2; 32 patients), or SOC (33 patients), and followed up for 28 days. There was an association with cough frequency after 10 days BREATHOX® compared to SOC [Group 1: hazard ratio (HR) 2.01, 95% confidence interval (CI) 1.06-3.81; Group 2: HR 2.17, 95% CI 1.17-4.04]. No differences between the groups for the reported symptoms' resolution time were seen after 28 days. After combining both BREATHOX® groups, the period to cough resolution 10 days after randomization was significantly lower than in SOC (HR 2.10, 95% CI 1.20-3.67). An adverse event occurred in 30% of Group 1, 36% of Group 2, and 9% in SOC individuals. One patient from SOC had a serious adverse event. Nasal burning, sore or itchy nose, and dry mouth were considered related to BREATHOX® use and resolved after stopping inhalations. (4) Conclusion: BREATHOX® inhalation is safe and may be effective in reducing the duration of COVID-19-induced coughing.

Elevator Ventilation and SARS-CoV-2-Relevant Particulate Matter Removal in Three Older California Elevators

The objective of this study was to measure particulate matter (PM) total loss rates in three older (1940s, 1960s, and 1980s) elevators in California during two phases and three low-cost intervention modes. Tracer gas decay and <2 μm aerodynamic diameter nontoxic NaCl particles (PM2) were used to calculate PM2 loss rates. The NaCl particles were considered surrogates for smaller particles carrying SARS-CoV-2. Empirical PM2 loss rates were paired with modeled dynamic scenarios to estimate SARS-CoV-2-relevant PM2 removal. Mean loss rates (hr-1) ranged from 1.8 to 184. Compared to a closed-door, stationary elevator, the moving elevators had a fourfold increased mean loss rate (hr-1), while an air cleaner in a stationary elevator increased the mean loss rates sixfold. In a dynamic particle removal simulation of a ten-story elevator, PM was removed 1.38-fold faster with an air cleaner intervention during bottom and top floor stops only (express ride) and 1.12-fold faster with an air cleaner during every other floor stops. The increase in removal rates due to the air cleaner was modest due to the higher moving and open-door removal rates, except during stationary phase. The half-life of PM2 particles in a stationary elevator after all passengers have left can be 8-12 minutes following a single emission and 2-5 minutes with an air cleaner. The low particle removal rate in the stationary elevator requires an intervention so that the particle removal rate will be high to eliminate infectious aerosol. If codes permit, keeping the door open when the elevator is stationary is most effective; otherwise, an air cleaner in a stationary elevator should be used. While an air cleaner is commonly seen as a substantial improvement in reducing potential virus concentration in air, in the moving elevator scenarios, the effect is quite modest. This paper provides empirical particle loss rates inside elevators, the effectiveness of air cleaners in a dynamic elevator space, two approaches to control infectious agents while the elevator is stationary, and support for a precautionary approach towards elevator use amidst a pandemic.

Development and Characterization of New Cathode Materials for Sodium-Metal Chloride Batteries

Solid metal halides are used as active cathode ingredients in the case of Na-NiCl2 batteries that require a fused secondary electrolyte, sodium tetrachloraluminate (NaAlCl4), to facilitate the movement of the Na+ ion into the cathode. The sodium-nickel chloride (Na - NiCl2) battery has been extensively investigated as a promising system for large-scale energy storage applications. The growth of Ni and NaCl particles in the cathodes is one of the most important factors that degrade the performance of the Na-NiCl2 battery. The larger the particles of active ingredients contained in the cathode, the smaller the active surface available for the electrochemical reaction. Therefore, the growth of Ni and NaCl particles can lead to an increase in cell polarization resulting from the reduced active area. A higher current density, a higher state of charge (SOC) at the end of the charge (EOC) and a lower Ni / NaCl ratio are the main parameters that result in the rapid growth of Ni particles.In light of these problems, cathode and chemistry Nano-materials with recognized and well-documented electrochemical functions have been studied and manufactured to simultaneously improve battery performance and develop less expensive and more performing, sustainable and environmentally friendly materials. Starting from the well-known cathodic material (Na-NiCl2), the new electrolytic materials have been prepared on the replacement of nickel with iron (10-90%substitution of Nichel with Iron), to obtain a new material with potential advantages compared to current battery technologies; for example, (1) lower cost of cathode material compared to the state of the art as well as (2) choices of cheaper materials (stainless steels could be used for cell components, including cathode current collectors and cell housings).The study on the particle size of the cathode and the physico-chemical characterization of the cathode was carried out in the test cell using, where possible, the GITT method (galvanostatic technique of intermittent titration). Furthermore, the impact of temperature on the different cathode compositions of the positive electrode was being studied. Especially the optimum operating temperature is an important parameter of the active material.

Sound Absorption Performance and Mechanism of Aluminum Foams with Double Main Pore‐Porous Cell Wall Structure

To enhance the sound absorption performance of open‐cell aluminum foam, the double main pores‐porous cell walls (DMP‐PCW) aluminum foams via infiltration casting of preforms mixed with two sizes of NaCl particles are prepared. The pore structure, sound absorption performance, and mechanism of DMP‐PCW aluminum foam are investigated. The pore structure consists of double‐sized main pores similar to the NaCl particles and the cell wall pores formed by the connections between NaCl particles. It is found that the static flow resistivity of DMP‐PCW aluminum foam reaches an optimum value of 28105 Pa.s m−2 when the volume proportion of small main pores increases, the size of cell wall pores decreases, and the number of cell wall pores per unit main pore surface area (NPPA) increases. At 800–6300 Hz, the average absorption coefficient is 0.89. In addition, the Wilson model predicts the sound absorption properties of DMP‐PCW aluminum foam. The predicted values agree well with the measured values. The finite‐element acoustic simulations and dynamic viscous‐thermal permeability calculations reveal that the improved sound absorption performance of DMP‐PCW aluminum foam is correlated to the enhanced sound transmission caused by increased NPPA and increased viscous‐thermal loss due to the double main pore structure.

Design and evaluation of a thermal precipitation aerosol electrometer (TPAE)

Abstract. A new aerosol electrometer (AE), the thermal precipitation aerosol electrometer (TPAE), was designed for use with particles of sizes less than 300 nm, and its performance was experimentally evaluated. The TPAE combines the thermal precipitator with a microcurrent measurement circuit board (i.e., pre-amplifier) for measuring the current carried by collected particles. The thermal precipitator is in the disk-to-disk configuration. Heating paste and air cooling were adopted to establish the desired temperature gradient in the precipitation chamber. At a sample flow rate of 0.3 L min−1 and a temperature gradient of 264 K cm−1, the precipitation efficiency of 70 nm particles reaches ∼100 %. The measurement range of the designed aerosol electrometer is ±5×105 fA, and the accuracy is ±2 fA (2500 to 6.25×107 cm−3 using a flow rate of 0.3 L min−1 and assuming that only singly charged particles exist in the sample). During the evaluation process, the electrical performance of the TPAE was first tested using sodium chloride (NaCl) and soot particles previously classified by a differential mobility analyzer (DMA) and compared to the reference. The precipitation performance of the TPAE was then characterized as functions of the temperature gradient, sampling flow rate and particle size. It was shown that the particle collection efficiency of the built-in thermal precipitator is inversely proportional to the sampling flow rate and proportional to the temperature gradient. The effect of particle size on the particle collection efficiency was minor for NaCl particles of sizes between 23 and 200 nm. Unlike that which was observed for the NaCl particles, a slightly positive correlation between the collection efficiency and the mobility size for soot particles (in the size range of 30–160 nm) was observed. This observation might be due to the existence of soot agglomerates. Compared to existing electrometers, the TPAE does not require the use of high-efficiency filters and includes the additional feature of the “soft” collection of particles for offline particle characterization as well as aerosol current measurement.

Low‐temperature synthesis of α‐Al2O3 powder aided by ball milling and a trace amount of sodium chloride

AbstractIt is crucial to synthesize α‐Al2O3, which is a multifunctional material, at high temperatures due to the nature of the material. However, this high‐temperature preparation process is not energy efficient, which goes against the global aim of carbon neutrality. In this study, we explored the effect of adding 1 wt.% (NaCl) as an additive and a suitable amount of Al(OH)3 in a ball mill to form a precursor. The impact of NaCl and ball milling duration on the phase transition from Al(OH)3 to α‐Al2O3 at low temperatures was investigated. After the conversion from Al(OH)3 to γ‐Al2O3, the NaCl particles on the surface of γ‐Al2O3 act as diffusion channels, helping to accelerate the substance diffusion during the transition from γ‐Al2O3 to α‐Al2O3, resulting in a lower formation temperature of α‐Al2O3, which is 700°C. Additionally, the presence of NaCl results in α‐Al2O3 particles growing into hexagonal plates. The α‐Al2O3 plates produced from calcining the mixture of Al(OH)3 and NaCl at 700°C have an average diameter of 3 µm, an average diameter/thickness ratio of 10 and a specific surface area of 12.0085 m2/g. These results indicate that low‐temperature synthesis of α‐Al2O3 powder is possible by using NaCl as an additive instead of molten salt in the ball milling process.

Nanotextured porous titanium scaffolds by argon ion irradiation: Toward conformal nanopatterning and improved implant osseointegration.

Stress shielding and osseointegration are two main challenges in bone regeneration, which have been targeted successfully by chemical and physical surface modification methods. Direct irradiation synthesis (DIS) is an energetic ion irradiation method that generates self-organized nanopatterns conformal to the surface of materials with complex geometries (e.g., pores on a material surface). This work exposes porous titanium samples to energetic argon ions generating nanopatterning between and inside pores. The unique porous architected titanium (Ti) structure is achieved by mixing Ti powder with given amounts of spacer NaCl particles (vol % equal to 30%, 40%, 50%, 60%, and 70%), compacted and sintered, and combined with DIS to generate a porous Ti with bone-like mechanical properties and hierarchical topography to enhance Ti osseointegration. The porosity percentages range between 25% and 30% using 30 vol % NaCl space-holder (SH) volume percentages to porosity rates of 63%-68% with SH volume of 70 vol % NaCl. Stable and reproducible nanopatterning on the flat surface between pores, inside pits, and along the internal pore walls are achieved, for the first time on any porous biomaterial. Nanoscale features were observed in the form of nanowalls and nanopeaks of lengths between 100 and 500 nm, thicknesses of 35-nm and heights between 100 and 200 nm on average. Bulk mechanical properties that mimic bone-like structures were observed along with increased wettability (by reducing contact values). Nano features were cell biocompatible and enhanced in vitro pre-osteoblast differentiation and mineralization. Higher alkaline phosphatase levels and increased calcium deposits were observed on irradiated 50 vol % NaCl samples at 7 and 14 days. After 24 h, nanopatterned porous samples decreased the number of attached macrophages and the formation of foreign body giant cells, confirming nanoscale tunability of M1-M2 immuno-activation with enhanced osseointegration.